title: Resonant inelastic X-ray scattering and X-ray absorption spectroscopy on the negative electrode material Li0.5Ni0.25TiOPO4 in a Li-ion battery.
abstract: We have studied the first lithiation/delithiation cycle of the Li-ion battery electrode material Li(x)Ni(0.25)TiOPO(4) applying X-ray absorption spectroscopy (XAS) and resonant inelastic X-ray scattering (RIXS). A set of ten identical Li(x)Ni(0.25)TiOPO(4) battery electrodes have been cycled and left in different states of charge in the range of x = 0.5 … 2.5, before disassembly in an Ar filled glove box. We find that Ni-, Ti-, and O-ions are affected simultaneously, rather than sequentially, upon lithiation of the material. In particular, Ni is reduced from Ni(2+) to Ni(0) but only partially re-oxidized to Ni(1+), again, by delithiation. Overall, there is considerable "crosstalk" between the different atomic species and non-linearity in the response of the electronic structure during the lithiation/delithiation process. Fortuitously, the background variation in Ni L-XAS shows to contain valuable information about solid-electrolyte interface (SEI) creation, showing that the SEI is a function of the degree of lithiation.
authors.affiliation: Department of Physics and Astronomy, Uppsala University, Box 516, SE-751 20, Uppsala, Sweden. hakan.hollmark@physics.uu.se
authors.forename: H M
authors.initials: HM
authors.lastname: Hollmark
authors.forename: K
authors.initials: K
authors.lastname: Maher
authors.forename: I
authors.initials: I
authors.lastname: Saadoune
authors.forename: T
authors.initials: T
authors.lastname: Gustafsson
authors.forename: K
authors.initials: K
authors.lastname: Edström
authors.forename: L-C
authors.initials: LC
authors.lastname: Duda